Cycles restarts render without prompt

I want to give feedback about weird issue. I was trying to render a heavy 10M polygon scene with gtx970 GPU,everything went well and render finishes. but suddenly it restarts the same render.

The scene is an interior shop scene with many linked objects,IES lights,lots of textures. my machine is old and it has 8gb of ram ,so I thought that this is the issue, but then I send the whole project to my friend who has very powerful pc and the same problem happens,cycles restarts the same render again.I didn’t use “render animation” command btw.

I know this issue could happen from various ways but could you help me to fix this problem?

Maybe you have multiple view layers that are all rendering?

This is more a question for the community forums though: